Where might one check in? Look left (7)
I believe the answer is:
airport
'where might one check in?' is the definition.
(as in checking in for a flight)
'look left' is the wordplay.
'look' becomes 'air' (something might have a certain air or look).
'left' becomes 'port' (left side of a ship - opposite of starboard).
'air'+'port'='AIRPORT'
(Other definitions for airport that I've seen before include "passenger terminal" , "Travel terminus" , "Liverpool's John Lennon, for example" , "O'Hare or Kennedy, say" , "Where to take flight" .)